Antenna deicing



Aug. 2, 1960 s. PICKLES ETAL 2,947,841

ANTENNA DEICING Filed April 6, 1959 IG-l United States Patent ANTENNA DEICING Sidney Pickles, P.0. Box 1126, Tonopah, Nev., and 'Reuben S. Tice, Monterey, Calif.; said Tice assignor to said Pickles Filed Apr. 6, 1959, Ser. No. 804,367 4 Claims. (Cl.219--10.79)

The present invention relates to method and means for removal of ice and the like from antennas and to the prevention of the formation of ice upon antennas.

In geographical areas where weather conditions are sufliciently severe to produce snow, sleet, or below freezing temperatures the accumulation of ice and snow upon antennas causes a substantial problem. Serious impairment of antenna gain may result from such accumulation and a consequent material interference with radio and television communication thereby results. Antenna icing may also cause impedance mismatching between antennas and transmission lines feeding same in the case of transmitting antennas so as to thereby detune a transmitter output circuit connected to the antenna and serious damage may even result to the output stage from such detuning.

Inasmuch as heavy antenna icing cannot be tolerated it has become customary, particularly for transmitting antennas, to provide hot elements thereon disposed at convenient spaced points on the antenna for the purpose of maintaining the over-all antenna temperature above freezing to prevent the accumulation of ice and snow upon the antenna surface. These hot elements conventionally comprise resistance heaters wherein resistance heating wire is electrically energized to produce heat by the conventional resistance energy dissipation therein proportional to the square of the energizing current times the resistance of the wire. Although the application of heat to antennas by conventional resistance heaters will accomplish the desired result of preventing undue icing of the antenna surfaces, yet various drawbacks are encountered in the use of such heaters for inasmuch as same are only conveniently spaced at separate points upon antennas, it is thereby necessary to maintain the temperature at the heater considerably higher than is required at that point in order that antenna surface areas remote from the heater will still be maintained at a temperature in excess of freezing. High temperature operation of resistance heaters, as is required in conventional antenna deicing systems, results in material wear of the heater itself, necessitating a substantial amount of maintenance which is highly undesirable for antenna systems.

The present invention provides antenna heating Without the difficulties attendant prior art devices. It is contemplated by the present invention that antennas of all types shall be heated to any desired temperature by inductive heating wherein there is induced upon the antenna surface eddy currents which operate to heat the surface as desired. The present invention operates to heat antennas without in any way interfering with the prime purpose of the antennas, i.e., radiation or receipt of electrical-energy through the atmosphere. Additionally, the present invention provides a manner of heating wherein the reluctance of the inductive circuit employedfor heating is minimized, to the end of thereby minimizing the driving current providing energy for raising the antenna temperature.

Patented Aug. 2, 1960 It is an object of the present invention to provide antenna heating means for uniformly heating the entire operative surface of an antenna to prevent accumulation of ice and snow thereon.

It is another object of the present invention to provide means for inducing a heating current upon antenna surfaces distributed substantially uniformly thereover to maintain a desired antenna temperature.

It is a further object of the present invention to provide means for uniformly heating antenna surfaces with a minimum of heating energy.

It is yet another object of the present invention to provide antenna heating means establishing eddy currents uniformly over the operating antenna surfaces to maintain a desired temperature thereof.

It is a still further object of the present invention to provide means for maintaining antenna temperatures at desired levels with a minimum of heating power.

It is an object of the present invention to provide means for inductively heating an antenna without interfering with antenna functions and employing a low reluctance circuit for the minimization of power required to maintain a desired antenna temperature level.

It is yet another object of the present invention to provide means for heating antenna surfaces by inducing eddy currents thereon wherein a maximum of input energy is converted into heat applied to the antenna surface.

Numerous other possible objects and advantages of the present invention will become apparent to those skilled in the art from the following description and drawing of a preferred embodiment of the invention. Although the invention is herein illustrated and described with respect to certain preferred embodiments thereof no limitation is intended thereby, but instead reference is made to the appended claims for a proper delineation of the true scope of the present invention.

The invention is illustrated in the accompanying drawings, wherein:

Fig. 1 shows a portion of a hollow antenna cylinder including antenna heating means of the present invention;

Fig. 2 shows a portion of a hollow antenna cylinder including a modified form of antenna heating means in accordance with the present invention; and

Fig. 3 schematically illustrates a folded dipole antenna including heating means in accordance with the present invention.

Considering now the present invention in some detail and referring to Fig. l of the drawings, there will be seen to be illustrated therein in foreshortened view, a hollow metallic cylinder 11 forming such as a radiating element or radiator of an antenna. In accordance with the present invention, there is disposed within the cylinder 11 a Winding 12 of insulated electrical conductor. This winding 12 is preferably disposed immediately adjacent the inner wall of the cylinder 11 in order to maximize inductive coupling between the winding and the cylinder. Electrical energization of the winding 12 is provided by alternating power supply current 13 connected by means of electrical conductors 14 and 16 to opposite ends of the winding 12. Actuation of the alternating power supply 13, as by means of integral switching therein, operates to pass an alternating current through the winding 12 within the cylinder 11. The alternating current passing through the winding 12 induces eddy currents upon the surface of the antenna 11 inasmuch as the winding and antenna cylinder are inductively coupled. Such eddy currents flowing upon the surface of the antenna cylinder will thereby operate to dissipate energy thereon in the form of heat. Such heat is proportional to the square of the current times the resistance of the eddy current paths and has been found quite effective to efliciently heat the antenna surface. It is to be noted as regards the antenna heating described above, that heating currents are induced substantially over the entire antenna surface so that therefore a uniform heating efiect results. In' contrast to prior known antenna heating systems, the prment invention thereby need attain a relatively lower temperature at any one point on the surface or on the heating means in order to maintain a constant temperature over the entire antenna surface. This is materially advantageous inasmuch as it minimizes heater damage and, at the same time, is highly desirable insofar as the antenna itself is concerned.

Although the embodiment of the invention described above and illustrated in Fig. 1 is'advantageous over prior artsystems for heating antenna surfaces, yet there remains the diiiiculty therewith that the magnetic circuit employed in inducing eddy currents upon the antenna surface has a relatively high reluctance so that substantial heating power is necessary to provide the desired heating effect. Inasmuch as antennas are conventionally formed of non-ferrous materials, the reluctance of the magnetic circuit employed to induce eddy currents in the antenna is necessarily high. In Fig. 2 of the drawings there is shown a modification of the present invention wherein the reluctance of the magnetic circuit is materially reduced so as to thereby provide with a minimum heating current a sufficiently large fiux density to cause substantial eddy currents upon the antenna surface.

Referring to Fig. 2 there will be seen to be illustrated therein a foreshortened view of a hollow metallic cylinder 11 forming a part of anantenna. Within the antenna cylinder ll there is disposed, preferably in concentric arrangement therewith, an elongated tube 21 formed of a ferrous material. This inner tube 21 is provided with at least one radial slot therein extending over the length thereof for the purpose of reducing or minimizing eddy currents thereon. The tube 21 may be mounted within the antenna in any suitable manner as, for example, by insulators or in certain installations by direct metallic contact wherein the antenna characteristics are not affected thereby. A coil winding 22 is disposed within the antenna cylinder 11 about the tube 21 and is formed of an electrical conductor having insulation thereabout. This coil 22 may be advantageously wound upon the ferrous tube 21 which thereby comprises, in addition to other functions, a coil form. To this end it is preferable that the tube 21 have only a single longitudinal slot therein in order that the structural rigidity and strength of the tube may not be materially impaired by such slot ting. An alternating current power supply 23 is connected as by leads 24 and as between opposite ends of the coil winding 22 to thereby energize same with an alternating current. As the coil 22 is wound substantially circumferentially of the antenna cylinder ii and the tube 21 it will be seen that upon passage of alternating current through the winding 22, same is inductively coupled both to the antenna cylinder ll and tube 21, with the former providing one side of the inductively coupled circuit and the latter the other. As the ferrous tube 21 has a low magnetic reluctance, the over-all reluctance of the magnetic circuit linking the winding 22 and the antenna cylinder 11 is thereby materially reduced through the insertion of the tube Zlwithin the winding. in this manner then there is provided a substantial reduction in the current required of the power supply 23 to accomplish any particular heating of the antenna cylinder ll. A very material and, in fact, major portion of the energy delivered to the winding 22 appears in the antenna as heat, so that there is provided by the present invention a relatively efiicient means for heating antennas.

Application of antenna heating to all types of antennas may be readily accomplished without major antenna modification. There is, for example, illustrated in Fig. 3 of the drawing a folded dipole antenna 31 having a radiofrequency input line '32 adapted to energize same for radiating energy from the antenna in a conventional manner. In accordance with the present invention there is provided an insulated inductive winding 33 disposed Within the cylindrical members of the dipole antenna 31 and extending substantially over the entire interior thereof. Winding energization is provided from an alternating current power supply 34 through electrical connectors 36 and '37 which are preferably brought into the antenna at the center of the top thereof which is known to be a zero voltage point for the radio-frequency energy applied thereto. Consequently, the winding 33, and the wiring 36 and 37 therefore, are disposed in such a manner as to be completely excluded from the radio-frequency field of the antenna. As may be seen from the Faraday efiect there is no radio-frequency field within the cylinders of the antenna so that the winding 33 is thereby separated from the radio-frequency field as are the input leads 36 and 37 which emerge from the antenna at a point of zero radiofrequency voltage. For ease of illustration, there has not been shown a ferrous tube or coil form in the dipole antenna '31 of Fig. 3. It will, of course, be appreciated that such an element may be readily disposed therein to thereby attain all of the advantages discussed above in connection with Fig. 2. Likewise, in other types of antenna such as, for example, the conventional Yagi, there is encountered no structural difficulty in modifying commercially available antennas to include the heating means of the present invention. In particular, this is true Wherein the coil form or tube such as the element 21 of Fig. 2 is employed upon which to wind the coil, for in such instance it is necessary only to provide the coil form and winding of appropriate dimension to slide within the radiation elements of the antenna. Connection of the heating coil'of the present invention to an external ener gizing source from any type of antenna is accomplished in accordance with conventional antenna practice by inserting the leads at points of zero radio-frequency voltage of the antenna.

What is claimed is:

1. An improved heated antenna comprising at least one hollow radiating element, an elongated ferrous coil form, an insulated winding adapted for insertion within a hollow antenna radiator in substantial coextension therewith and wound about said form in inductive relation thereto, and

, means extending from said coil for energizing same with an alternating current whereby a low reluctance magnetic pathlinks said winding and antenna and heating currents are effectively induced in said antenna.

2. An improved heated antenna comprising at least one hollow cylindrical antenna radiator, an elongated ferrous member within said radiator, an insulated multiturn electrical Winding disposed upon the surface of said ferrous member within said radiator about the interior surface thereof and extending over the length thereof, said Winding being disposed in inductive relationship to said ferrous member and radiator, and electrically conducting means extending from said winding exterior to said radiator and adapted for connection across an alternating current power supply for energization of said winding to induce heating currents in said radiator.

3. A deicing antenna comprising a plurality of hollow radiating elements, a plurality of electrically conducting insulated windings disposed individually within said radieting elements in inductive relation thereto, electrical connections extending from opposite ends of said wind-:

ings exteriorly of said radiating elements at points of zero radio-frequency voltage'thereof and adapted for connection across an alternating current power supply whereby energization of said windings thereby induces eddy currents upon the surface of said radiating elements to heat same uniformly thereover.

4. An improved heated antenna comprising at least one hollow radiating element, an insulated electrical winding disposed within said radiating element substantially coextensive therewith and adjacent the interior wall thereof, References Cited in the file of this patent an elongated hollow ferrous member disposed within said UNITED STATES PATENTS winding and having at least one slot longitudinally thereof, and electrical leads extending from opposite ends of 23 2 g 11111639 1 said winding exteriorly of said radiating element for con- 5 f z nection to a source of alternating current whereby enerme man 959 gization of said winding thereby induces through a 10W reluctance path including said ferrous member eddy cur- FOREIGN PATENTS rents upon said radiating element to uniformly heat same. 863,223 Germany J an. 15, 1953 

